Production of iron-oxide pigments



' Patented Sept. 2, .1930

Jumps Lnux', or TUERDi'NGEilI-QN-THEQRHIN E, GERMAKY, ggiwqghfl f NDUSTRIE KrI NeEsnLLscH rr, or rnnn ronnonrnnyiyrnrn, 'qnrnriAN'Y S oo'nronnrron vor GERM NY rs i w r r IBPN-QXIFDE new i No Drawing. Original application 'filed Septem er-7, 192 6, seria1'mi134,12a, and in qermany, Au' ustao,

1 i925. Divided and this application filed September s ,-192 7. ,fs ria1'1wq. 15,353. a

The present invention relates to processes for the production ofiron oxide pigments, more specifically, thelinventio'n. relates to a process in which a finely, divided iron hy- 'droxide is obtained as a by-product from the reduction of aromatic nitro compounds by means of iron and acids'or acid reacting.

salts. The invention also embraces the new products. o

In the methods of producing aromatic -which lies between Fe O and ,Fe203.' This oxide is not useful as a color pigmentand is of very inferior quality on account of. its

. low coloring power. v i 7 v As I have set forth in'my co-pending application for U. S. Patent, Serial Number" 106,969, filed on May 5, 1926, finely divided iron oxides or iron hydroxides of high commercial value are obtained, ifthe reduction is carried out under such-conditions thatthe aqueous phase of the reaction mixture is a highly concentrated saltsolution.

I have foundfurther, that if the salt pr'esent in the solution contains aluminum as metallic base, solutions of lower concentration, and even highly diluted solutions, likewise give good results. 1 4

According to the present invention, the re duction of; aromatic ;nitro compounds with iron metal is carried out in the presence of a V dilute aqueous solution of an aluminum salt. A ready made solution of such a salt may be employed, to which a further addition of 40 known hydrolysis of aluminum salts leading to the production of sufli cient free acid for; the reduction. The aluminum salt may, how-2 ever, also be produced during the reaction, i. e., by the addition tothe required quantity of iron of acertain quantit be a particularlysuitable salt. 1

amines heretofore known and used for a long cination.

acid maybe unnecessary on account of the V are reduced in solution of 18 k'gs.iof a'lumiof metallic. aluminum. -For the purpose 0 this inven 7 tion aluminum chloride has been found to out in this man n r inthe pr s n eof a iluted alum num salt "solution (the processnot essentially {deg- I parting in otherrespects from the customary for example,aniline, resulting from; the-nitrq compound, a slurry which zcontainsfthfe; 02 i? i .dized iron as a finely divided yellow. hy-

droxide of the trivalent iron oxide Fe O Afterlevigation, washing out. drying, this hydroxide is useful as a color; pigment;

either directly or,if .re'd shades arerlesfired,

after being subjected to a -preliminarycala The'processisillustrated by th I examples. It is to be:understoohh howeveny that'the'process accordingto the present.in}v a.

vention is capable of beingcarried out :with

other nitro icom'pounds'than those mentioned,

in' these examples; :for example, with chlor-..; hydroXy-, ahd'amino-nitro compounds, poly-j nitro compounds, and nitro siilfonic ,acids Other aluminum salts can be'use'd in place of the chloride. Besides the aluminum sailt,

the solutions may contain other solluble salts in low concentration-.,

Example 1.-2OO kgs; of nitrobenzene V are allowed to runat" 100 65, int o 25.0"kg-s. of

a solutionlof aluminumfchloride (AilCl g andQOO kgs} of ground iron. The temper-a.-

turemaintains itself at 100 C; due to the l: heat ofjreaction. When the reduction is fin ished the'resulting aniline is separatd inv the well known mannerg There remains (a y ell owish brown slurry," which is separated from th e' excess of metallic ironandjdriedq con sists of an iron hydroxidezhav ing an average content of 12% of combinedwater. By calcinationit is converted into'adeep'viole'tfred,

ironoxidepigment. i

nuni chloride in 310 k gsl of water; with 200. kgs. ofv iron. After .distillationzof the orthotfllidine -ye low;hydroxideor ironi-ha'ving arwatler cont ntv of about 1.2% is obtainedfrom the residues, which product,

n lisa ing p 500 1.0... yields a .bri lien f a red iron oxide is obtalnedp wam'ple3.200 kgs. of nitronaphthalene are reduced in a'solution of 20 kgs. of aluminum chloride, 4 kgs. of water and kgs.

- by means of solvents. The remaining yellow residues are freed from any remaining sol-' vents by treatment with steamfth'en Washed".

andcentrifuged. By calcinationa brilliant Example 4.200 kgs. of nitrobenzene are 'reduced inAOO kgsrofja 7.5%v aqueous solu- 'tion of. hydrochloric acidrby means of 220 kgs. of iron and 6 kgs. of aluminum metal.

In the course of the reaction aluminum chloride is formed. The iron hydroxi'de which isobtained as a by-product of the reduction has nearly the sameproperties as in the fore- 'goingl example." The quantity and concentration of the hydrochloric acid used may be varied Within wide limits; e. g., less than the 'amountequivalent to the aluminum metal can be used. I v r r p This application isa division of my co- 1 pending application Ser. No. 134,123, filed Sept.7,1926.

Iolaim:

I 1. In the process of reducing an aromatic- 'n1tro compound involving the treatment of the nitrocompound with a reducing agent 1 comprising iron andan agent which is hydrolyzable in water to produce hydrogen ions,

to the production ofithe correspondingamine andan iron oxide sludge, the steps which conslst 1n uslng as the reducing agent a IIIIX- ,,ric acid in amount insuflicient to dissolve the iron and reacting with the aluminum and other ingredients to improve the pi'gmenting properties of the resulting iron oxide sludge, separating the said resulting sludge from the reaction mixture, and purifying the former by levigation and washing out.

4.1n the processof reducing an aromatic nitro compound involving the treatment of the nitro compound with a reducing agent comprising iron and an agent Which is hydrolyzable in water to produce hydrogen ions, to the production of the corresponding. amine and an iron oxide sludge, the steps which consist in using as the reducing agent a mixture of iron, aluminum metal and hydrochloric acid in amount insufficient to dissolve the iron and reacting with the aluminum and other ingredients to improve the pigmenting properties of the resulting iron oxide sludge, separating the said resulting sludge from the reaction mixture, purifying the former by levigation and washing out, and drying and calcining the resulting product.

vIn testimony whereof, I aflix my signature.

JULIUS LAUX.

tureof iron, aluminum metal and an acid in amount-insufficient to dissolve the 1ron and reacting with the aluminum and other ingredients .to improve the pigmenting prop erties of the resulting iron oxide sludge, sepa-. rating the said resulting sludge from the reaction mixture, and purifying the former by levigation and washing out. 7

2.;Inthe process of reducing an aromatic nitro compound involvlng thetreatment. of

- the nitro compound with a reducing agent comprising iron and an agent which is hydrolyzable in water to produce hydrogen ions,

to the production ofthe corresponding amine and an iron oxide sludge, the steps which consist in using as the reducing agent a mixture of iron, alumlnum metal and an acid in 7 amount insufiicient to dissolve the iron and reacting with the aluminum and other ingredients to improve the pigmenting properties of the resulting iron oxide sludge, separatingthe said resulting sludge from the reaction mixture,purifying the former by levigation and washingout, and drying and calcining the resulting product. 3; In theprocess of'reducing aromatic nitro compounds involving the treatment of the nitro compound with a reducing agent com prising iron and an agent which is hydro- 

